1. Field of the Invention
This invention relates to chalk line apparatus of the type having a spool that is rotated around an axis to selectively pay out and retrieve line.
2. Background Art
Chalk lines are used for projects by those in the construction trades as well as those that engage in hobbies that require “snapping” of a straight line of chalk. To accomplish this, a string laden with chalk is tensioned between two points on a surface and then “snapped” to cause the chalk to be deposited upon that surface.
Commonly, a supply of string is controlled using a chalk line apparatus having a housing that defines a chamber within which a reel and a supply of chalk are contained. Through a handle, the reel can be turned around an axis in one direction to wrap the string around a spool on the reel. By exerting a force on a portion of the string that projects from an opening through the housing, the reel can be rotated oppositely to the one direction to allow the string to be paid off of the spool.
The string within the housing chamber is exposed to the supply of chalk, thereby to allow adherence of the chalk thereto. The chalk supply is ideally loosely contained within the chamber so that as the housing is moved, the chalk cascades over the spool and the string wrapped therearound. The repeated exposure of the string to the loose chalk assures that there is a proper coating of the string that allows consistent quality lines to be “snapped”.
Heretofore, the reels for the supply of line have been made with a cylindrical spool centered upon the rotary axis for the reel. Spaced, disc-shaped flanges, at the axial ends of the spool, determine the axial dimension of the string storage space.
With this conventional construction, as the spool is rotated to retrieve string, the string wraps around the outer spool surface to produce a progressively increasing cylindrical shape.
This conventional design has one significant drawback. The substantially constant cylindrical configuration of the outer spool surface, and the string that is progressively built up thereupon, tends to interact with the chalk supply, in which the spool and string are at least partially immersed, in a manner that the reel with the string thereon tends to “cavitate”. With the chamber completely full of chalk, the rotating reel, with the string thereon, tends to form a cylindrical cavity in the accumulated chalk of progressively increasing diameter. As this occurs, there is a slight radial compaction of the chalk at the inwardly facing cavity edge that tends to maintain this edge intact. This compacted chalk tends to block passage of chalk to against the string wrapped around the spool.
With the string fully retrieved, the cavity has its maximum diameter. As string is paid off of the reel, the effective diameter of the spool with the string wrapped therearound progressively decreases. The reel may continue to rotate, in this manner, potentially without any significant amount of chalk migrating towards the spool and the string wrapped therearound. The end result may be that there is an inadequate coating of chalk on the string, which may account for a poor quality line or necessitate retrieval of the line and repeating of the steps carried out to initially snap the line.
While the above problem is potentially overcome by having the user shake the housing to break free chalk that is compacted to produce the cavitation effect, users may not routinely do this. Even if they do, having to perform the additional step is an inconvenience that ideally one would not have to contend with while using a chalk line apparatus.
Still further, this condition may be aggravated by environmental conditions. For example, in high humidity environments, or when working with the chalk line apparatus in snow or rain, the chalk retains moisture that may make it more susceptible to compacting in the housing chamber to cause the cavitation effect, described above.
Ideally, users of chalk line apparatus would be able to repeatedly retrieve and pay out string to produce high quality lines without having to take any special steps to avoid the above problem.